1. Field of the Invention
The invention relates to a fuel reserving device and, in particular, a fuel tank connected to an engine.
2. Description of the Related Art
A fuel reserving device or fuel tank should be in communication with the outside air such that the surface of the fuel can rise and fall in the fuel tank. In the fuel tank, fuel vapor may be generated in a space formed above the fuel surface. Therefore, the problem of the discharge of fuel vapor from the fuel tank to the outside air arises.
In a prior art, a fuel tank is in communication with the outside air via a charcoal canister for temporarily adsorbing fuel vapor thereon. The charcoal canister must be large if the amount of the fuel vapor generated in the fuel tank is large. To solve this problem, unexamined Japanese patent publication No. 64-16426 discloses a fuel tank comprising an inflatable airbag therein, the airbag being inflated or deflated according to the change of the level of the fuel surface to prevent a space being formed above the surface of the fuel in the fuel tank.
However, in the fuel tank disclosed in the above publication, the interior of the fuel tank is not in communication with the outside air. Therefore, if a space has been already formed above the fuel surface, the space cannot be eliminated when the airbag is inflated. Thus, fuel vapor may be generated in the space above the fuel surface.
Therefore, the object of the invention is to eliminate the space above the fuel surface, and the fuel vapor therein, from the fuel reserving device.